Generally these are used to convey a similar message as a pie chart (already supported), but can be much easier to read. One reason they are easier to read is that treemap in the shape of square/rectangle with width of X can use more visual space than a circle with diameter of X.
Well, that kind of a treemap is also implementable. It’s just that you have to code the algorithm to make those SVG nodes yourself. Which may be tricky.
I’ve had pretty good success with QuickChart and setting up a table-embedded chart is really simple. @David_Kossnicktipped me off and I’ve refined the process to make it really easy.